There are untold instances in the fluid flow field where it is desirable to discriminate between liquid and gaseous flow. This is particularly true in the production of hydrocarbons from oil wells where artificial lift is employed. Where the specific artificial lift apparatus is a rod pump, the downhole pump can usually lift fluid at a greater rate than the hydrocarbon bearing formation can release it into the wellbore. Therefore, the fluid level in the wellbore will decrease with each stroke of the pump, until the pump piston lifts clear of the fluid on the upstroke. Under this condition, as the pump piston descends on the downstroke, it will pound into the fluid, causing shock waves to be transmitted through the sucker rods to the surface equipment. This is called a "pump-off" condition and is injurious to the downhole pump, rod string, as well as the pump jack apparatus. An aggravated pump-off condition induces severe "fluid pounding."
When an oil well is "pumped-off," liquid flow decreases and gaseous flow increases. Accordingly, an effective pump-off control must incorporate a flow sensor which is capable of differentiating between a liquid and gaseous flow condition.
In my prior issured U.S. Pat. Nos. 3,551,071 and 3,551,620, there is taught a Flow, No-Flow device for discriminating between liquid and gaseous flow. Reference is made to these two previously issued patents as well as to the prior art cited therein for further background of the invention.
The present invention constitutes improvements over the prior art in that the addition of a manifold and a rearrangement of the porting associated with the movable valve element brings about unexpected results which greatly increases the utility of the prior art apparatus.
The present invention can be used to advantage in conjunction with wells operated by a computer control system by placing the apparatus of the invention in a flow line, and determining whether oil or gas is flowing therethrough. A remote alarm means can be actuated by the flow responsive apparatus to pin point the precise well which is off production.